Letter to Editors

Wittig Rearrangement of Lithiated Allyl Aryl Ethers: A Mechanistic Study

“…The bulk of the material was obtained without isomerization in form of the silanes 1a (58 %) and 1b (70 %) along with the bis(silanes) 2a (6.5 %) and 2b (9.4 %) as by-products resulting from a twofold metalation at both the α-allyl and an ortho-aryl position (Scheme 4). No other new compounds, in particular no (3aryl-2-propenyloxy)trimethylsilanes derived from [1,4] migration products 4, were identified.…”

“…The manifold of mechanistic possibilities is multiplied when allyl entities are involved as either the stationary or the migratory group. [1][2][3][4][5][6] In addition to the ubiquitous [1,2] migration pattern, three more rearrangement modes can thus become operational by connecting the [1,4], [3,2] or [3,4] sites (as shown in the center of Scheme 1). Scheme 1.…”

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) Whereas the [3.2] mode offers the opportunity to accomplish stereocontrolled carbon-carbon linking reactions and is therefore synthetically most attractive, [3][4][5] the [1.2] mode was in the focus of numerous mechanistic studies. [1,6] The principal features of the structural reorganization of α-(alkoxy)alkyllithiums are nowadays widely accepted (Scheme 2).…”

Evidence for a loop mechanism of protein transport by the thylakoid Delta pH pathway

“…Biochemical and genetic studies show that there are two pathways for protein entry into the lumen, the cpSec pathway and the Delta pH pathway. Precursor proteins transported by the cpSec pathway have similar transport requirements as exported bacterial proteins ; ATP, the proton motive force, and a chloroplast homologue of the bacterial SecA protein (cp-SecA) [2,3]. A plant thylakoid SecY homologue (cpSecY) is presumed to function in thylakoid transport in cooperation with cpSecA [4].…”

[1,3]‐Transfer of Chirality during the Nicholas Reaction in γ‐Benzyloxy Propargylic Alcohols

“…[4] In this regard, the [2,3]-Wittig rearrangement of ethers has also come under close scrutiny as a carbon-carbon bond-forming reaction of potential application to the stereodirected synthesis of acyclic alcohols. [5] Chirality transfer during [2,3]-sila-Wittig rearrangements allows the stereoselective formation of SiÀC bonds. [6] In the literature, very efficient chirality transfers in acyclic systems have also been achieved from chiral heteroatoms to carbon derivatives, [7] and in chiral metal complexes, [8] palladium(0)-promoted intra-and intermolecular allylation reactions, [9] and [3,3]-sigmatropic rearrangements of allylic acetates catalyzed by palladium(ii).…”